In the use of copper casting molds for the continuous casting of steel melts, premature damage occurs in the presence of zinc and/or sulfur in the thermally most highly stressed contact regions with the steel melts.
In this context, zinc as a component, for example, of molten automobile scrap (zinc as corrosion protection) reacts with the hot copper surface, and, in a diffusion process, it forms brittle α/β/γ brass phases. These split off, and as a result they lead to crack formation.
Sulfur, which is present, for instance, because of auxiliary casting materials, reacts with copper to form high volume and brittle copper sulfides. These may split off too. The notch effect created by local corrosion in this respect is consequently an ideal starting point for the formation of cracks.